The present invention relates to a collecting hood for capturing the exhaust air above cooking areas, production devices and the like, said collecting hood including a vapor chamber, an extraction chamber and an air supply chamber which extend horizontally and parallel to one another in a longitudinal direction, wherein                the vapor chamber is downwardly open and tapers upward,        the extraction chamber is separated from the vapor chamber by a filter or a separator, wherein the filter or the separator forms an inclined boundary of the upwardly tapering vapor chamber, and        the air supply chamber tapers downward and merges at its bottom end into a curved deflection region which opens out into a discharge opening which is arranged at a bottom end of the vapor chamber opposite the extraction chamber such that supply air, which is blown from above into the air supply chamber, emerges from the discharge opening horizontally or upwardly at an angle in the direction of the filter or of the separator.        
A collecting hood of this type, as is described, for example, in U.S. Pat. No. 3,978,777, is significantly more efficient when capturing exhaust air than collecting hoods of a more simple design which only have an extraction means. A preferred area of use relates to large kitchens in the catering sector, wherein cooking areas in this context can be any kitchen devices in which capturing the exhaust air is necessary or desirable, that is ovens, grills, roasters, deep fat fryers, etc. In this case, the exhaust air to be captured above all includes water vapor, oil and grease. The use of such collecting hoods, however, is not limited to cooking areas, they can also be used, for example, for capturing exhaust air in the case of production processes of any kind, in particular in the foodstuff industry or even in industrial manufacturing.
The principle of operation of collecting hoods of this type proceeds from the general problem that the range of the suction action of an extraction chamber is relatively limited such that, in the case of collecting hoods which operate exclusively with extraction means, a relatively large proportion of the exhaust air captured in the vapor chamber passes the extraction chamber and the filter or separator and is not immediately extracted. The exhaust air captured in this way stays in the vapor chamber a very long time and rotates inside said vapor chamber in a rolling flux until it is captured by the extraction chamber and extracted. Consequently, a directed air flow, which runs from the discharge opening to the filter or separator and, in so doing, crosses the vapor chamber in which the ascending exhaust air is collected, is generated by means of the air supply chamber. Said air flow captures the exhaust air such that it flows in a very effective manner through the filter or the separator into the extraction chamber and there can be extracted quicker than in the case of the conventional collecting hood without an air supply chamber.